Hurricane Milton went from barely hurricane strength to a dangerous Category 5 storm in less than 24 hours as it moved across the Gulf of Mexico toward Florida.

As wind speeds increased, Milton became one of the fastest intensifying storms on record. And with sustained winds of 300 km/h on October 7, 2024 and very low pressure, it also became one of the strongest storms of the year.

Less than two weeks after the devastating impact of Hurricane Helene, this type of storm was the last thing Florida wanted to see. Hurricane Milton was expected to make landfall as a major hurricane late October 9 or early October 10 and had already prompted widespread evacuations.

What exactly is rapid intensification, and what does global climate change have to do with it? We research the behavior of hurricanes and teach meteorology. Here’s what you need to know.

What is rapid intensification?

Rapid intensification is defined by the National Weather Service as an increase in a tropical cyclone’s maximum sustained wind speed of at least 30 knots – about 35 mph (55 km/h) within a 24-hour period. That increase could be enough to escalate a storm from Category 1 to Category 3 on the Saffir-Simpson scale.

Milton’s wind speed went from 80 mph to 170 mph from 1 p.m. Sunday to 1 p.m. Monday, and the pressure dropped from 988 millibars to 911.

The National Hurricane Center already warned that Milton was likely to become a major hurricane, but this kind of rapid intensification could catch people off guard, especially if the hurricane occurs close to landfall.

Hurricane Michael caused billions of dollars in damage in 2018 when it quickly grew into a Category 5 storm just before hitting Tyndall Air Force Base in the Florida Panhandle. In 2023, Hurricane Otis’ maximum wind speed increased by 100 mph (160 km/h) in less than 24 hours before hitting Acapulco, Mexico. Hurricane Ian also rapidly intensified in 2022 before hitting just south of where Milton is expected to cross Florida.

What causes hurricanes to intensify quickly?

Rapid intensification is difficult to predict, but there are some driving forces.

• Ocean Heat: Warm sea surface temperatures, especially as they extend into deeper layers of warm water, provide the energy needed to intensify hurricanes. The deeper the warm water, the more energy a storm can harness, increasing its strength.

• Low wind shear: High vertical wind shear – a rapid change in wind speed or direction with height – can disrupt a storm’s organization, while low wind shear allows hurricanes to grow faster. In Milton’s case, atmospheric conditions were particularly conducive to rapid intensification.

• Moisture: Higher sea surface temperatures and lower salinity increase the amount of moisture available for storms, causing rapid intensification. Warmer water provides the heat needed to evaporate moisture, while lower salinity helps retain that heat close to the surface. This allows more persistent heat and moisture to be transferred to the storm, making the storm faster and stronger.

• Thunderstorms: Internal dynamics, such as bursts of intense thunderstorms within a cyclone’s rotation, can reorganize a cyclone’s circulation and lead to rapid strength gains, even if other conditions are not ideal.

Research has shown that worldwide, a majority of Category 3 and higher hurricanes tend to rapidly intensify during their lifetime.

How does global warming affect the strength of hurricanes?

If it seems like you’ve been hearing about rapid intensification a lot more often in recent years, that’s partly because it’s becoming more common.

A 2023 study examining the links between rapid intensification and climate change showed an increase in the number of tropical cyclones experiencing rapid intensification over the past four decades. That includes a significant increase in the number of hurricanes that rapidly intensify several times during their development. Another analysis comparing trends from 1982 to 2017 with climate model simulations found that natural variability alone could not explain this increase in rapidly intensifying storms, pointing to a likely role of human-induced climate change.

How future climate change will affect hurricanes is an active area of ​​research. As global temperatures and oceans continue to warm, the frequency of major hurricanes is expected to increase. The extreme hurricanes of recent years, including Beryl in June 2024 and Helene, are already raising alarms about the increasing impact of warming on the behavior of tropical cyclones.

This article is republished from The Conversation, an independent nonprofit organization providing facts and trusted analysis to help you understand our complex world. It was written by: Zachary Handlos, Georgian Institute of Technology and Ali Sarhadi, Georgian Institute of Technology

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Zachary Handlos receives funding from the National Science Foundation. He is affiliated with the American Meteorological Society as the new chairman of their Board on Higher Education. He is also an academic faculty affiliate of the Georgia Climate Project.

Ali Sarhadi receives funding from NSF and Georgia Tech.